immobilize cadmium from aqueous solutions and we Sorption of cadmium from aqueous solutions on several cal-could localize the sites of the crystal structure of the cium hydroxyapatites was investigated as a function of pH and apatite in which cadmium is sorbed. The results suggested of the concentration of cationic vacancies, using elemental and that, under our experimental conditions, the main sorpstructural analysis. The main result is that the maximum uption mechanism is an ion exchange process. More retake of cadmium into the apatitic framework is about 0.8 mol/ cently, using measurements performed by a nuclear mimol and does not depend on the stoichiometry of the starting croprobe (13), it was shown that cadmium really diffuses solid. Sorbed cadium is localized in the 6h sites of the structure into the bulk of apatite crystals, confirming that diffusion adjacent to the channels including the OH groups. For the less and ion exchange are the main mechanisms. A pH stoichiometric apatite (1.1 cationic vacancy per mol), the same dependant modification of the apatite stoichiometry also phenomenon takes place, but a dissolution-precipitation mechtakes place during sorption ( 14). In our experiments, the anism is added, thus increasing the total quantity of cadmium maximum uptake of cadmium which could be achieved immobilized in the solid. The additional sorbed quantity corresponds to the precipitation of Cd 5 H 2 (PO 4 ) 4 . Such results may be was about 0.8 mol per mol of apatite. This concentration used for the treatment of contaminated waters and industrial is far from the value expected from the number of wastes.